WASHINGTON (AP) — Senate Republicans on Wednesday blocked the confirmation of federal appeals court nominee Caitlin Halligan for the second time, denying President Barack Obama a key judicial appointment.

A majority of senators, 51, supported Halligan's nomination, but Democrats needed 60 votes in the 100-member Senate to get it past Republican objections.

Citing her work on lawsuits against gun manufacturers and on behalf of illegal immigrants, Republicans said Halligan is too liberal to sit on the U.S. Court of Appeals for the District of Columbia. The National Rifle Association opposed her nomination.

Obama said he was "deeply disappointed" in the Senate's action.

"Ms. Halligan has always practiced law with the highest ethical ideals, and her qualifications are beyond question," Obama said. "Furthermore, her career in public service and as a law enforcement lawyer, serving the citizens of New York, is well within the mainstream."

Democrats said the effort to block Halligan, who was first nominated to the appeals court in September 2010 to fill the seat vacated by John Roberts when he was elevated to chief justice of the Supreme Court in 2005, also is about maintaining a conservative majority on a key appellate court. GOP senators blocked the confirmation vote on her in December 2011 and Obama renominated her in January this year.

There are currently four vacancies on the court, with nominees from Republican presidents holding a slim, 4-3 majority. The D.C. appeals court is considered one of the most important courts in the country because it handles challenges to most federal rulemaking and oversees federal agencies based in Washington.

The Washington court is also something of a pipeline to the Supreme Court. Four of the nine the justices on the Supreme Court served on the D.C. Circuit before being confirmed to the higher court: Chief Justice John Roberts and Justices Antonin Scalia, Clarence Thomas and Ruth Bader Ginsburg.

"Lets call it for what it is," said Sen. Chuck Schumer, D-N.Y., supporting Halligan's nomination. "This has to do with keeping a court with the same views."

Republicans defended their votes to block Halligan, saying they objected to Halligan in particular, not the idea of a Democratic nominee to the key court. Citing her work as the state of New York's solicitor general, Sen. Charles Grassley said Halligan could not be trusted.

"This is a court where we can least afford to nominate an activist judge," he said.

Republican Leader Mitch McConnell called Halligan's former work as solicitor general for the state of New York "a textbook example of judicial activism."

"The point here is that even in cases where the law was clear, or the courts had already spoken, including the Supreme Court, Ms. Halligan chose to get involved anyway, using arguments that had already been rejected either by the courts, the legislature, or, in the case of frivolous claims against the gun manufacturers, by both," McConnell said.

McConnell cited two cases Halligan worked on when she was New York state's solicitor general. In one, Halligan filed a brief to the Supreme Court arguing that the National Labor Relations Board should have the legal authority to grant back pay to illegal aliens. In another, Halligan argued that that gun manufacturers contributed to a public nuisance of illegal handguns in the state.

In a letter to lawmakers, the NRA expressed similar concerns with Halligan's work on gun issues.

Halligan served as New York state's solicitor general from 2001 to 2007. Halligan is now general counsel in the Manhattan District Attorney's Office.

Sen. Lisa Murkowski of Alaska was the only Republican who voted in favor of advancing Halligan's nomination. Senate Democratic Leader Harry Reid of Nevada switched his vote to side with Republicans near the end of the roll call as a parliamentary move that allows him to bring her nomination up again for a vote sometime in the future.

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